scholarly journals Temporal and Spatial Dynamics of Primary and Secondary Infection by Armillaria ostoyae in a Pinus pinaster Plantation

2004 ◽  
Vol 94 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Brigitte Lung-Escarmant ◽  
Dominique Guyon
Keyword(s):  
Pinus Pinaster ◽  
Secondary Infection ◽  
Spatial Dynamics ◽  
Spatial Relation ◽  
Gompertz Model ◽  
Inoculum Density ◽  
Initial Inoculum ◽  
Primary Inoculum ◽  
Armillaria Ostoyae ◽  
Epidemic Development

Epidemiological investigations were performed in a 3-ha maritime pine (Pinus pinaster) plantation established on a site heavily infested by Armillaria ostoyae. Geostatistics were used to examine the density and the distribution of the initial inoculum. Disease dynamics were monitored for 17 years after planting. On the whole site, the cumulative mortality rate reached 35% over this period, plateauing at 12 years. Disease progress curves differed according to the density of the initial inoculum, although in all the cases, the Gompertz model described the epidemics well. The epidemiological contributions of both primary (initially colonized stumps) and secondary inoculum (newly dead pines) were evaluated by analyzing their spatial relation to annual mortality. Newly dead pines acted as secondary inoculum from year 3 and their role increased with time. When the initial inoculum density was low, the contribution of secondary inoculum to epidemic development increased faster and halted sooner than when the density of primary inoculum was high. Regardless of its density, the primary inoculum acted throughout the dynamic phase of the epidemic. When the inoculum density was low, the probability of mortality during the first 6 years of the epidemic depended on the tree distance from the nearest stumps colonized by Armillaria sp. When the inoculum density was high, the probability of mortality was higher and not related to the distance between trees and colonized stumps.

scholarly journals Influence of Inoculum Density of Verticillium dahliae on Root Discoloration of Horseradish

Plant Disease ◽  
2000 ◽  
Vol 84 (3) ◽  
pp. 309-315 ◽  
Author(s):  
A. Khan ◽  
N. Atibalentja ◽  
D. M. Eastburn
Keyword(s):  
Verticillium Dahliae ◽  
Commercial Production ◽  
Inoculum Density ◽  
Forecast System ◽  
Factors Affecting ◽  
Initial Inoculum ◽  
Disease Forecast ◽  
Low Levels ◽  
Negative Exponential ◽  
The Relationship

The relationship between inoculum density (number of microsclerotia per gram of air-dried soil) of Verticillium dahliae at the time of planting and the severity and incidence of root discoloration of horseradish at harvest was investigated in a 2-year study conducted in the greenhouse, microplots, and commercial production fields. The objective of the study was to develop a disease-forecast system that would assist growers in assessing the risk of the disease before planting horseradish in a particular field. Significant correlations were observed between inoculum density and severity and incidence of root discoloration in the greenhouse and microplots, although the form of the relationship varied with trials from linear to quadratic and negative exponential. No correlation was found between inoculum density of V. dahliae and severity and incidence of root discoloration in commercial production fields. In some fields with low inoculum densities, high ratings of severity and incidence of root discoloration were observed even with the partially resistant cultivar 769A. Conversely, in other fields with high inoculum densities, low ratings of severity and incidence of discolored roots were observed even with the susceptible cultivar 647A. These results suggest that a disease-forecast system based solely on inoculum densities of V. dahliae would be unreliable under field conditions when the other factors affecting the inoculum density-disease relationships cannot be controlled. Knowing the amount of initial inoculum may, however, save growers from planting horseradish in highly infested fields, but it would not guarantee a disease-free crop in fields with low levels of infestation.

scholarly journals Optimization of culture conditions for in vitro adventitious roots and selected flavonoids production in Boesenbergia rotunda liquid suspension culture

Food Research ◽  
2020 ◽  
Vol 4 (S5) ◽  
pp. 26-33
Author(s):  
K.A. Ghani ◽  
A. Yusuf ◽  
N. Khalid
Keyword(s):  
Adventitious Roots ◽  
Ph Value ◽  
Culture Conditions ◽  
Inoculum Density ◽  
Root Production ◽  
Initial Inoculum ◽  
Perennial Plant ◽  
Liquid Suspension ◽  
Boesenbergia Rotunda

Boesenbergia rotunda (L.) Mansf. is one of the unique monocotyledonous perennial plant species belonging to the ginger (Zingiberaceae) family. Locally known as ‘Temu Kunci’ in Malaysia and Indonesia, this medicinal plant has been widely used in Asian dishes, particularly as a condiment or as traditional natural medicines. The important medicinal properties of B. rotunda majorly derived from flavonoids which are highly sought as pharmaceuticals. In this study, culture conditions for the growth of adventitious roots in liquid suspension cultures were optimized. The highest adventitious root production was achieved when cultured with initial inoculum density of 1.5 g and pH value at 5.8 after five weeks of culture. HPLC analysis discovered that production of valuable flavonoid compounds (pinostrobin, cardamonin and panduratin A) was significantly higher when the adventitious roots were cultured with initial inoculum density of 1.5 g whereas the initial pH medium did not significantly affect flavonoid production.

scholarly journals Relationship Between the Inoculum Density of Verticillium dahliae and the Progress of Verticillium Wilt of Olive

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1372-1378 ◽  
Author(s):  
F. J. López-Escudero ◽  
M. A. Blanco-López
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Disease Incidence ◽  
Olive Tree ◽  
Temporal Variations ◽  
Inoculum Density ◽  
Infested Soil ◽  
Initial Inoculum ◽  
Progress Curve ◽  
Olive Trees

An experiment was conducted in microplots which were artificially infested with a defoliating isolate of Verticillium dahliae using seven different treatments of inoculum densities ranging from 0 to 10 microsclerotia per gram of soil (ppg). The experiment was conducted in Andalucía (southern Spain), and the susceptible Spanish olive cv. Picual was used to determine the relationship between pathogen inoculum density and the progress of Verticillium wilt of olive (VWO). The inoculum, produced on a sodium pectate cellophane medium, was found to efficiently infect olive trees. Symptoms first appeared 30 weeks after the trees were transplanted into infested soil. Periods of increasing disease incidence in the following seasons and years were mainly during spring and autumn, particularly in the second year after planting. Olive trees exhibited a high susceptibility to the defoliating pathotype of the pathogen, even at very low inoculum levels; in fact, diseased plants were encountered throughout the experiment regardless of the inoculum density treatment. Inoculum densities greater than 3 ppg in the soil resulted in final disease incidence greater than 50% for the trees after 2.5 years. Therefore, these inoculum densities must be considered very high for olive trees. There were no differences in final disease incidence, mean symptom severity, or area under the disease progress curve between plots infested with 10 or 3.33 ppg, whereas other treatments exhibited lower values for each of these disease parameters. The temporal variations of disease incidence and severity were highly correlated for the higher inoculum density treatments, with r2 values ranging from 0.92 to 0.84 for disease incidence and from 0.93 to 0.88 for severity. However, r2 was slightly lower for the treatments involving lower inoculum densities of the pathogen in microplots. The slopes of the linear regression curves were statistically different for nearly all the inoculum density treatments. Positive correlation was found between the initial inoculum density and final disease incidence values after the study period that was accurately explained by mathematical models. The results suggest that susceptible olive cultivars should not be planted in soils infested with virulent defoliating pathotypes of V. dahliae. Results also clarify that inoculum density levels obtained from field soil analyses can be used for establishing a risk prediction system with a view to controlling VWO in olive tree plantations.

scholarly journals Dynamics of Primary and Secondary Infection in Take-All Epidemics

1999 ◽  
Vol 89 (1) ◽  
pp. 84-91 ◽  
Author(s):  
D. J. Bailey ◽  
C. A. Gilligan
Keyword(s):  
Winter Wheat ◽  
Initial Phase ◽  
Primary Infection ◽  
Adventitious Roots ◽  
Secondary Infection ◽  
Inoculum Density ◽  
Separate Experiment ◽  
Disease Progress ◽  
Seminal Roots ◽  
Take All

Using a combination of experimentation and mathematical modeling, the effects of initial (particulate) inoculum density on the dynamics of disease resulting from primary and secondary infection of wheat by the take-all fungus, Gaeumannomyces graminis var. tritici, were tested. A relatively high inoculum density generated a disease progress curve that rose monotonically toward an asymptote. Reducing the initial inoculum density resulted in a curve that initially was monotonic, rising to a plateau, but which increased sigmoidally to an asymptotic level of disease thereafter. Changes in the infectivity of particulate inoculum over time were examined in a separate experiment. Using a model that incorporated terms for primary and secondary infection, inoculum decay, and host growth, we showed that both disease progress curves were consistent with consecutive phases dominated, respectively, by primary and secondary infection. We examined the spread of disease from a low particulate inoculum density on seminal and adventitious root systems separately. Although seminal roots were affected by consecutive phases of primary and secondary infection, adventitious roots were affected only by secondary infection. We showed that the characteristic features of disease progress in controlled experiments were consistent with field data from crops of winter wheat. We concluded that there is an initial phase of primary infection by G. graminis var. tritici on winter wheat as seminal roots grow through the soil and encounter inoculum, but the rate of primary infection slows progressively as inoculum decays. After the initial phase, there is an acceleration in the rate of secondary infection on both seminal and adventitious roots that is stimulated by the increase in the availability of infected tissue as a source of inoculum and the availability of susceptible tissue for infection.

scholarly journals Population dynamics of botanical epidemics involving primary and secondary infection

1997 ◽  
Vol 352 (1353) ◽  
pp. 591-608 ◽  
Author(s):  
Christopher A. Gilligan ◽  
Adam Kleczkowski
Keyword(s):  
Fungal Infection ◽  
Mycorrhizal Fungi ◽  
Plant Pathogens ◽  
Initial Conditions ◽  
Secondary Infection ◽  
Generic Model ◽  
Direct Transmission ◽  
Initial Inoculum ◽  
Special Cases ◽  
Host Growth

In this paper we study the dynamical properties of models for botanical epidemics, especially for soil–borne fungal infection. The models develop several new concepts, involving dual sources of infection, host and inoculum dynamics. Epidemics are modelled with respect to the infection status of whole plants and plant organs (the G model) or to lesion density and size (the SW model). The infection can originate in two sources, either from the initial inoculum (primary infection) or by a direct transmission between plant tissue (secondary infection). The first term corresponds to the transmission through the free–living stages of macroparasites or an external source of infection in certain medical models, whereas the second term is equivalent to direct transmission between the hosts in microparasitic infections. The models allow for dynamics of host growth and inoculum decay. We show that the two models for root and lesion dynamics can be derived as special cases of a single generic model. Analytical and numerical methods are used to analyse the behaviour of the models for static, unlimited (exponential) and asymptotically limited host growth with and without secondary infection, and with and without decay of initial inoculum. The models are shown to exhibit a range of epidemic behaviour within single seasons that extends from simple monotonic increase with saturation of the host population, through temporary plateaux as the system switches from primary to secondary infection, to effective elimination of the pathogen by the host outgrowing the fungal infection. For certain conditions, the equilibrium values are shown to depend on initial conditions. These results have important consequences for the control of plant disease. They can be applied beyond soil–borne plant pathogens to mycorrhizal fungi and aerial pathogens while the principles of primary and secondary infection with host and inoculum dynamics may be used to link classical models for both microparasitic and macroparasitic infections.

scholarly journals Absence of Oospores of Downy Mildew of Grape Caused by Plasmopara viticola as the Source of Primary Inoculum in Most Western Australian Vineyards

Plant Disease ◽  
2005 ◽  
Vol 89 (7) ◽  
pp. 777-777 ◽  
Author(s):  
B. X. Killigrew ◽  
K. Sivasithamparam ◽  
E. S. Scott
Keyword(s):  
Downy Mildew ◽  
Secondary Infection ◽  
Plasmopara Viticola ◽  
The State ◽  
Annual Rainfall ◽  
Infected Leaf ◽  
Wine Grape ◽  
Primary Inoculum ◽  
The North ◽  
Plant Pathol

Grapevine downy mildew, caused by the obligate, oomycete pathogen, Plasmopara viticola, was first recorded in Western Australia (W.A.) in 1998 (2) and has subsequently been observed in most viticultural regions of the state. Heterothallism in P. viticola was established by Wong et al. (3), whereby more than one mating type of the pathogen is required for sexual reproduction to occur. Oospores are considered to be the source of primary inoculum for this disease with further, secondary infection being advanced by asexual inoculum. However, recent research in European vineyards suggests that the majority of infection throughout the growing season arises via sexually derived (oosporic) inoculum (1). Since downy mildew is relatively new to W.A., few surveys have been conducted to study populations of the pathogen within the state. It is also noteworthy that the incidence of oospores in Australian vineyards has not been reported. The objective of this research was to assess the occurrence and type of inoculum of P. viticola in W.A. vineyards. A total of 1,266 P. viticola-infected leaf discs (LD) from eight wine-grape (775 LD), five table-grape (450 LD), and seven unknown (41 LD) cultivars grown in 16 vineyards in 10 geographically separate regions of W.A. were collected in the growing seasons of 2001-2003. These regions range from Chittering in the north to Albany in the south and received 700 to 1,200 mm annual rainfall, mostly in winter. Each LD was cleared in 1 M KOH at 60°C for 12 to 24 h and then was assessed for the presence of oospores with light microscopy. Leaves showing “mosaic”-type lesions (older infection) late in the season were collected where possible to ensure colony maturity and an increased likelihood of oospore formation. All LD from all regions were negative for the presence of oospores except for samples from a single vineyard (approximately 1,200 mm annual rainfall), where all 140 LD from six wine-grape cultivars contained oospores. The discovery that oospores were present in only one of 16 sampled vineyards provides a rare opportunity to study gene flow in field populations of the pathogen with time and to determine sources of primary inoculum where overwintering of P. viticola may not involve oospores. References: (1) S. McKirdy et al. Plant Dis. 83:301, 1999. (2) A. Rumbou et al. Eur. J. Plant Pathol. 110:379, 2004. (3) F. P. Wong et al. Plant Pathol. 50:427, 2001.

scholarly journals Plasmodiophora brassicae Inoculum Density and Spatial Patterns at the Field Level and Relation to Soil Characteristics

Pathogens ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 499
Author(s):  
Andrea Botero-Ramirez ◽  
Sheau-Fang Hwang ◽  
Stephen E. Strelkov
Keyword(s):  
Soil Properties ◽  
Spatial Patterns ◽  
Soil Ph ◽  
Plasmodiophora Brassicae ◽  
Spatial Dynamics ◽  
Inoculum Density ◽  
Soil Parameters ◽  
Soilborne Disease ◽  
Field Level ◽  
Calcium And Magnesium

Clubroot, caused by Plasmodiophora brassicae, is an important soilborne disease of the Brassicaceae. Knowledge of the spatial dynamics of P. brassicae at the field level and the influence of soil properties on pathogen spatial patterns can improve understanding of clubroot epidemiology and management. To study the spatial patterns of P. brassicae inoculum density and their relationship to different soil properties, four clubroot-infested fields in central Alberta, Canada, were sampled in 2017 and 2019, and P. brassicae inoculum density, soil pH, and boron, calcium, and magnesium concentrations were quantified. Spatial autocorrelation of the inoculum density was estimated for each of the fields in both years with the Moran’s I and semi-variograms. A Bayesian hierarchical spatial approach was used to model the relationship between P. brassicae inoculum density and the soil parameters. Patchiness of the pathogen was detected, with most patches located at the field edges and adjacent to the entrance. Infested patches grew in size from 2017 to 2019, with an average increase in diameter of 221.3 m and with this growth determined by the maximum inoculum density and active dispersal methods such as movement by machinery and wind. Soil pH, boron, calcium, and magnesium concentrations were not found to have an important effect on the inoculum density of P. brassicae.

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